Make branches in notification setting support regex (similar to paths)

[vlad-ko]

Example of how this is working in "paths":
https://docs.codecov.com/docs/ignoring-paths

From the customer:
We'd like to roll out patch coverage PRs for only my team first so we can test at smaller scale before potentially rolling out to more devs at our company. So we'd like patch to apply to all branches like:

feature/branch1
feature/branch2
...
teammate2/branch3

without needing to update the codecov.yml with the specific name of the branch. This would make it work automatically for my team but not for other devs on other teams. For example feature/* as a regex would cover all of my branches since I always prefix them with feature.

This is where we'd like to add regex support:
https://docs.codecov.com/docs/notifications#standard-notification-fields